Folic acid-coupled phosphorylated Fe2+ chelating peptide: The properties of Fe2+ chelating capacity and mechanisms of anti-gastrointestinal enzyme degradation

The aims of this study were to investigate the effect of precise phosphorylation of Ser in GL-Hyp-GPSGEEGKR on its Fe 2+ chelating capacity, and the effects and mechanisms of folic acid coupling to GL-Hyp-GPS (PO4) GEEGKR on its resistance against degradation by gastrointestinal enzymes. The results demonstrated that GL-Hyp-GPS (PO4) GEEGKR exhibited significantly enhanced Fe 2+ chelating capability compared to GL-Hyp-GPSGEEGKR. This was attributed to the phosphorylation of Ser introducing more Fe 2+ chelating sites. Furthermore, the results of UV–Vis, FTIR, and 1 H NMR showed that folic acid has successfully coupled with GL-Hyp-GPS (PO4) GEEGKR to generate folic acid-GL-Hyp-GPS (PO4) GEEGKR. Folic acid-GL-Hyp-GPS (PO4) GEEGKR demonstrated superior resistance against degradation by gastrointestinal enzymes. This may be attributed to the coupling of folic acid altering the original zeta potential of the peptide and the steric hindrance effect of folic acid hindering the interaction between enzymes and peptide. These findings can provide valuable insights for the production of high Fe 2+ chelating peptides that resist gastrointestinal enzyme degradation.